1. Field of the Invention
The invention relates to a filter, particularly to a dynamic filtering device and method thereof.
2. Description of the Related Art
In order to improve signal quality, a low-pass filter is usually introduced to eliminate noise when a circuit receives a time-variant signal to perform circuit measurement. In the process of digital signal processing, the low-pass filter can be implemented with a finite impulse response (FIR) filter or an infinite impulse response (IIR) filter. In general, the stability of FIR filters is better than that of IIR filters, but the noise immunity of the IIR filters is better than that of the FIR filters. With the same filtered result or performance, the hardware cost of the IIR filter is usually lower than that of the FIR filter.
However, response times of conventional filters vary with frequencies. The better the noise immunity the longer the response time will be, as shown in FIG. 1A. By contrast, when a short response time is required for a system, such as a touch panel performing position detection, the noise immunity will be sacrificed to gain the shorter response time as shown in FIG. 1B, where a touch position D (x, y) is a function of a x-coordinate and a y-coordinate. Therefore, conventional circuit designers believe that the response time needs to be traded off for the noise immunity in filter design.